1. Field of the Invention
The present invention relates to a pneumatic tire.
2. Description of the Related Art
Recently, in a tire market, e.g., the European market, there is a need for improvement of handling and stability including handling performance, high-speed lane changing performance, and the like of a pneumatic tire (hereafter referred to as “tire”), as performance of vehicles increases. For the improvement of the handling and stability, a tire having an asymmetric tread pattern and continuously extending land portions has been proposed. When the tire having the asymmetric tread pattern is mounted to the vehicle, the tire is disposed so that the tire tread pattern has a smaller groove area ratio on the outside portion of a tread area, the outside portion having a significant influence on the handling and stability, and a larger groove area ratio on the inside portion of the tread area. In this way, the tire having the asymmetric tread pattern can achieve the improvement of the handling and stability while maintaining performance during traveling on a wet road.
Moreover, in order to further enhance the handling performance of the tire, the continuously extending land portions between circumferential grooves of the tire are widened to thereby increase tread stiffness. However, if the continuously extending land portions are widened, the land portions are subject to uneven contact pressure, i.e., higher contact pressure in edge areas of each of the continuously extending land portions and lower contact pressure in inner areas. This results in unevenness of the contact pressure. As a result, high-speed lane change and handling are not necessarily performed smoothly and the high-speed lane changing performance and the handling performance may not be improved in some cases.
On the other hand, there is a known tire for improving cornering performance of a vehicle and stability for straight traveling at a high speed (Japanese Patent Application Laid-Open No. 2002-29216).
On this tire, a land portion is defined on a tread portion by grooves intersecting a cut section of the tread portion along a tread width, contact faces of the land portion are formed in curved shapes protruding radially outward along the tread width, and top portions of the contact faces which are the closest to an outline of a tread surface extending throughout the tread width are displaced toward one side edges of the land portion with respect to a center of a width of the land portion by distances 0.1 to 0.4 times the width of the land portion. In this way, the stability for straight traveling is expected to be improved advantageously while other performance such as drainage performance and a ride comfort including noise, vibration and harshness is maintained.